The invention relates to techniques for grounding electrical and telecommunication networks which are, at least in part, carried by utility poles, and to a pole support system for use with the grounding method.
All electrical, telecommunication, and cable TV distribution networks (aerial or buried) require that all components within these systems have a reference ground for their proper operation under normal use and to also provide electrical protection when faults occur. These faults may include, but are not necessarily limited to:
1. Failure of components within the system;
2. Thunder storms (lightning strikes);
3. Trees or debris falling on electrical conductors (wind and ice storms):
4. Vehicle collisions (car and truck) with the outside plant (poles, pedestals); and
5. Failure of components on customer premises (private substations, major faults within factories etc.)
Conventional grounding of these outside plant distribution networks is accomplished mainly by connecting all common ground components of all service providers on a given pole to the neutral wire (usually belonging to the electrical utility company) and running a common wire down the pole. This wire is then put to ground where it should provide an efficient common ground for the proper operation of the service provider networks and to ensure that any power surges will be shunted to earth as quickly and efficiently as possible.
Thus the efficiency of protection will depend largely on the quality of the wire""s electrical bond (wire running down the pole) with the earth. This electrical bond is established through mechanical means. Acquiring and maintaining quality, earth bonds have always challenged the industry.
Conventionally, industry has used galvanized ground rods (xc2xe inch diameter by 6 to 8 feet in length) which are hammered into the earth at approximately 16 to 18 inches from the pole. Using a mechanical clamp (sometimes a welded connection) the ground wire is attached. This technique has always given generally unsatisfactory results. The reasons for this being:
1. Rods offer relatively small surface area bonds with the soil thus electrical conductivity is limited (higher impedance);
2. A good portion of the rod (approx. ⅓) resides in relatively dry earth near the surface (conductively is thus limited);
3. Rods protrude and are a safety hazard for people;
4. The connection to the clamp is subject to damage (intentional or accidental); and
5. Rods tend to rust at the surface level and must be replaced periodically (approx. every 8 to 10 years depending on soil conditions).
It is also known from U.S. Pat. No. 2,645,048, issued Mar. 13, 1951 to Salmons, to use a pole butt ground plate consisting of a flat plate which approximates the shape of the butt of the pole and having a plurality of triangular prongs extending therefrom and cut from the material of the plate. Since the prongs engage ground on both sides, a better ground is said to be provided as compared with a butt plate which does not have such prongs. Furthermore, the prongs are said to keep the pole butt from shifting in the hole while the fill is being replaced around the pole during installation. It has been found that in installations utilizing wooden utility poles such as shown in U.S. Pat. No. 2,545,048, creosote is exuded from the bottom end of the pole which tends to flow along and coat surfaces nearest the bottom of the pole, particularly horizontal surfaces of such bearing plates, resulting in decreased grounding efficiency. A further problem with such bearing plates is that they tend only to make contact with the soil/ground at or immediately adjacent th bottom of the hole. When the holes for utility poles are drilled or otherwise excavated in the ground there remains at the bottom of the hole a significant amount of disturbed soil/ground consisting of loose debris which has fallen to the bottom of the hole as well as soil/ground at the bottom of the bole which has been agitated by the excavation process. Such soil/ground which has been disturbed does not provide the best contact with the plate for grounding purposes as it is not as compact as the undisturbed soil beneath the hole. The disturbed ground is also m re oxygenated which promotes rusting of the bearing plate.
Reference is made to Applicant""s prior U.S. Pat. No. 5,108,068, issued Apr. 28, 1992, and in a corresponding PCT Appilcaton No. PCT/CA92/00177, filed Apr. 27, 1992, both entitled Support System for Free Standing Poles or Posts, and both incorporated herein in their entirety by reference. Therein is described a pol anchoring system comprising one or more collars each having a plurality of blades or flukes pivotably connected thereto. An installation instrument is used to deploy the collar(s) within a hole and to extend the blades of the collar(s) in a generally radial direction causing the blades to penetrate the walls of the hole and thus securing the support collar therein. The pole is then inserted through the collar(s) whereby the collar(s) provide the necessary support to the base of the pole to resist lateral and/or rotational forces. The blades, which are extended into undisturbed soil around the hole, provide a substantial surface area to distribute the exerted forces. Applicant""s system replaces the traditional double-keying technique and eliminates the need for guy wires or push braces (and the associated additional real estate required therefor) which clutter the landscape and unavoidably tear up the surrounding soil. In using this system, no excavation of the poles location is required other than a hole slightly larger than the diameter of the pole, drilled to plant the pole or post in the ground using standard drilling methods now in use.
Applicant has realized that by fitting the base of the pole with a base support which can penetrate the generally undisturbed ground or soil at the bottom of the drilled hole when the pole is lowered, not only can additional lateral resistance be provided but the installation process can be shortened and thus made more efficient.
In general, the base support has a relatively large surface area for presentation against the applied forces which act on the pole in both rotational and lateral/transverse directions. The base support includes means for attaching it at or near the base of the polo and any leading edges can be angled to facilitate penetration into the generally undisturbed soil/ground xe2x80x9cbelowxe2x80x9d the bottom of the hole.
By connecting the pole""s electrical ground wire to an electrically conductive base support, an efficient grounding electrode is provided which will save both time and money for the industry and provide safer and more reliable services to the population.
More specifically, there is provided a method for the electrical grounding and support of a pole or post in a hole provided in undisturbed ground, the hole having disturbed ground at the bottom thereof beneath which is undisturbed ground, said method comprising:
providing a conductive base support whose surfaces are oriented predominantly in the vertical direction,
attaching a ground wire to said conductive base support;
attaching the conductive base support at or near the bottom of the pole or post prior to its installation in the hole in the ground such that at least a portion of the conductive base support extends below the bottom of the pole or post;
installing the pole or post in the hole such that the portion of the conductive base support which extends below the bottom of the pole or post penetrates the undisturbed ground beneath the disturbed ground at the bottom of the hole; and
connecting the ground wire to the electrical system of the pole or post.
There is also provided a combination pole support and electrical grounding arrangement for a pole being installed in a hole in undisturbed ground, the hole having disturbed ground at the bottom thereof beneath which is undisturbed ground, comprising:
a conductive base support whose surfaces are oriented predominantly in the vertical direction;
connection means for attaching a ground wire to said base support;
means for fastening the base support at or near the base of a pole such that at least a portion of the conductive base support extends below the bottom of the pole;
said portion of the conductive base support extending a sufficient length so as to be penetrable into the undisturbed ground beneath the disturbed ground at the bottom of the hole and so as to be engageable with the undisturbed ground beneath the hole to resist lateral and/or rotational forces exerted on the pole after installation.
The advantages in using such a conductive base support as a grounding electrode are:
1. The base support offers 4 to 5 times more surface area bonding with the soil than traditional grounding rods, thus electrical conductivity is optimized (lower impedance);
2. The base support resides entirely in generally undisturbed, cool moist earth under the pole which is approximately 5 to 10 feet underground (depending on the depth the pole is set), thus electrical conductivity is optimized (lower impedance). The undisturbed earth also tends to provide greater resistance against movement of the support and, hence, the pole or post;
3. No portion of the base support, nor its connection to the wire, is exposed to potential damage;
4. The possibility of base support rusting is minimal as there is very little oxygen to promote oxidation at 5 to 10 foot depths, especially in undisturbed soil/ground beneath the bottom of the hole (whereas soil/ground which has been exposed or which has been used as fill will have relatively high oxygen content). Thus the base support should match the life expectancy of the pole; and
5. The base support doubles as support for the foot of the pole and thus increases its stability in the soil (helps prevent the pole from leaning under transverse loads or from twisting under rotational loads).
Typically, in applications involving electric utility poles, grounding is effected at regular pole intervals and on each pole having a transformer. Accordingly, there is an enormous potential for a highly efficient, readily implementable grounding technique.
Further features and advantages of the invention will become more apparent from the following description of the preferred embodiment when taken in connection with the accompanying drawings.